White blood cells are an important part of your body’s immune system. They’re vital to protecting you from invading bacteria, viruses, and parasites. Your bone marrow produces all five of the different kinds of white blood cells in the body. Each white blood cell lives anywhere from several hours to several days in the blood stream. An eosinophil is a type of white blood cell. Eosinophils are stored in tissues throughout the body, surviving for up to several weeks. The bone marrow continually replenishes the body’s white blood cell supply. The number and type of each white blood cell in your body can give doctors a better understanding of your health. Elevated levels of white blood cells in your blood can be an indicator that you have an illness or infection. Elevated levels often mean your body is sending more and more white blood cells to fight off infections. An eosinophil count is a blood test that measures the quantity of eosinophils in your body. Abnormal eosinophil levels are often discovered as part of a routine complete blood count (CBC) test. Ongoing research continues to uncover an expanding list of roles performed by eosinophils. It appears now that nearly every system of the body relies on eosinophils in some way. Two important functions are within your immune system. Eosinophils destroy invading germs like viruses, bacteria, or parasites such as hookworms. They also have a role in the inflammatory response, especially if an allergy is involved. Inflammation is neither good nor bad. It helps isolate and control the immune response at the site of an infection, but a side effect is tissue damage around it. Allergies are immune responses that often involve chronic inflammation. Eosinophils play a significant role in the inflammation related to allergies, eczema, and asthma.
Why do I need an eosinophil count?
Your doctor may discover abnormal eosinophil levels when a white blood count differential is performed. A WBC differential test is often done alongside a complete blood count (CBC) and determines the percentage of each kind of white blood cell present in your blood. This test will show if you have an abnormally high or low count of white blood cells. White blood cell counts can vary in certain diseases. Your doctor may also order this test if they suspect specific diseases or conditions, such as:
- an extreme allergic reaction
- a drug reaction
- certain parasitic infections
How do I prepare for an eosinophil count?
There are no special preparations necessary for this test. You should inform your doctor if you’re taking any blood-thinning drugs such as warfarin (Coumadin). Your doctor may advise you to stop taking certain medications. Medications that may cause you to have an increased eosinophil count include:
- diet pills
- interferon, which is a drug that helps treat infection
- some antibiotics
- laxatives that contain psyllium
Before the test, be sure to tell your doctor about any current medications or supplements you’re taking.